Year	Number
1972	23327120
1973	23597576
1974	23983252
1975	23732104
1976	23512284
1977	23354196
1978	23375362
1979	23480802
1980	23295008
1981	23299972
1982	24219418
1983	24501582
1984	25288356
1985	26061888
1986	26741624
1987	28060556
1988	28961708
1989	30507590
1990	32102956
1991	32260636
1992	33846300
1993	35025672
1994	35397912
1995	34995316
1996	35827648
1997	34708900
1998	35485380
1999	36399312
2000	35665912
2001	34532344
2002	32547876
2003	31004656
2004	29630042
2005	28102352
2006	26466764
2007	25252248
2008	22713864
2009	22976516
2010	23800000
2011	23000000
2012	22500000
2013	22100000
2014	21500000
2015	22200000
2016	22300000
2017	22500000
2018	23600000